The Green-band luminescence (GL) from an Al-doped 4H-SiC Homoepitaxial layer prepared by using chemical vapur deposition (CVD) has been observed and studied. The deep pattern obtained by SEM and the buffer layer can be found in the interface between SiC substrate and epilayer. The deep profiles of Si atom in 4H-SiC epilayers obtained by using the secondary ion mass spectrometry (SIMS) and the X-ray photoelectron spectroscopy (XPS) show the relative distribution of Si and C. The results strongly suggest that the vacancy of C and the extended defects (point defects, threading dislocations, et al) from buffer layer are responsible for the GL emission. The full width at half maximum (FWHW) of GL indicates the distributions of VC and its complex defects. The quality of crystals and the distribution of defects in epitaxial layers can be characterized by the intensity and the wavelength of GL obtained from samples at room temperature.